Microactuators are miniaturized objects produced in solid supports, which may be semiconductors or insulators, for the purpose of forming microsystems such as, for example, microvalves or micropumps in fluid microcircuits, or microswitches in electronic microcircuits.
Microactuators using electrostatic, piezoelectric, electromagnetic and bimetallic effects have already existed for some time. A new generation of microactuators has started to appear, namely those using a pyrotechnic effect. In this regard, patent WO 98/22719 discloses a miniature valve for filling the reservoir of a transdermal administration device. The operating principle of this valve is based on the fragmentation of a substrate caused by the combustion gases from a pyrotechnic charge, said substrate initially separating a fluid reserve from an empty reservoir. This microvalve may, according to another embodiment, be used with an inflatable envelope. The combustion gases firstly cause the substrate to rupture and then the envelope to inflate for the purpose of pushing on a fluid so as to evacuate it. These microvalves have the double drawback of emitting substrate fragments into the microcircuit and of mixing the combustion gases with the fluid that they are supposed to release.
U.S. Pat. No. 4,111,221 discloses a non-miniaturized valve for interrupting, just once, the flow of a fluid between three concurrent ducts. This valve system includes a gas generator for inflating a bladder that is interposed at the intersection between the three ducts in order to completely close the fluid circuit. Various embodiments using in particular a piston that deforms the bladder under the action of gases are also present in the above document.